Remove a few buggy CodeMirror parameters

In particular, line numbers seem to be inexplicably broken in CodeMirror
when enabled in this plugin.

Also sets the height of the .CodeMirror to 'auto'.

Bug: Issue 8114
Change-Id: Ib7cd1f5d74418d6fa0e2a6b16b06ccd77090e06c

gr-editor/gr-editor.html

diff --git a/gr-editor/gr-editor.html b/gr-editor/gr-editor.html
index 9ff47d1..e1b0ba2 100644
--- a/gr-editor/gr-editor.html
+++ b/gr-editor/gr-editor.html
@@ -19,13 +19,15 @@
 <dom-module id="gr-editor">
   <template>
     <style include="gr-editor-styles">
-      .CodeMirror,
       #wrapper {
         height: 100%;
         z-index: 0;
       }
       .CodeMirror {
         font-family: 'Roboto Mono', Menlo, 'Lucida Console', Monaco, monospace;
+        height: auto;
+        /* CodeMirror has a default z-index of 4. Set to 0 to avoid collisions with fixed header. */
+        z-index: 0;
       }
     </style>
     <div id="wrapper"></div>

gr-editor/gr-editor.js

diff --git a/gr-editor/gr-editor.js b/gr-editor/gr-editor.js
index d75f7bd..4621fe7 100644
--- a/gr-editor/gr-editor.js
+++ b/gr-editor/gr-editor.js
@@ -52,7 +52,7 @@
     },
 
     getCodeMirrorParams(type, value, prefs) {
-      const params = {value};
+      const params = {value, viewportMargin: Infinity};
 
       if (prefs) {
         // TODO: Add gerrit's customizations from java codemirror to javascript
@@ -66,7 +66,8 @@
         // TODO(kaspern): Add support for keymaps.
         // params.keyMap = prefs.key_map_type.toLowerCase();
         params.lineLength = prefs.line_length;
-        params.lineNumbers = prefs.hide_line_numbers;
+        // Line numbers are currently broken. See Issue 8114.
+        params.lineNumbers = false;
         params.lineWrapping = prefs.line_wrapping;
         params.indentWithTabs = prefs.indent_with_tabs;
         params.matchBrackets = prefs.match_brackets;
@@ -74,10 +75,8 @@
         // Support for this is somewhere in gerrit's codebase
         // needs backporting to javascript
         params.mode = prefs.syntax_highlighting ? this._mapFileType(type) : '';
-        params.origLeft = value;
         params.showTabs = prefs.show_tabs;
         params.showTrailingSpace = prefs.show_whitespace_errors;
-        params.styleSelectedText = true;
         params.tabSize = prefs.tab_size;
         // TODO(kaspern): Add support for themes.
         // params.theme = prefs.theme.toLowerCase();